1. Field of the Invention
The invention relates to mixers, such as integrated circuit (IC) mixers. More particularly, the invention relates to mixers having multiple local oscillator (LO) inputs.
2. Description of the Related Art
Mixers are widely used in radio communication devices. Mixers often are used to perform frequency translation to either a lower operating frequency, i.e., a downconverter, in receivers, or a higher operating frequency, i.e., an upconverter, in transmitters. With mixers, both downconversion and upconversion is performed with the aid of a local oscillator. Typically, mixers operating at radio frequency (RF) and microwave frequencies exist as part of an integrated circuit (IC) mixer to perform frequency conversion.
In multi-channel devices, e.g., multi-channel receivers and multi-channel transmitters, it often is desirable to use the same type of IC mixer in each channel of the multi-channel design, e.g., for economic reasons and for operating performance reasons. Similarly, it often is desirable to use the same type of IC mixer in both the receiver and transmitter of a transceiver.
In such applications, it is typical to have a common local oscillator (LO) signal drive the mixer for the mixer's use in each channel. Because of this, many conventional IC mixers typically allow for only one local oscillator input pin or one input point into the IC package. However, in the physical layout of a printed circuit board (PCB), such configuration often is less than optimal, especially in applications where the same type of mixer is used for multiple channels. In such applications, the local oscillator signal often has to be routed around the integrated circuit and/or routed to a different layer of the circuit board, e.g., using a via, or the local oscillator signal has to be routed directly underneath the mixer to supply the local oscillator signal to the appropriate local oscillator input pin.
Conventional IC mixers include an IC mixer that accepts two local oscillator inputs, and switches internally between the two inputs based on the desired operating frequency band. However, although such configuration can offer adequate frequency performance, such configuration often is not well suited to improving the overall physical layout of a printed circuit board containing multiple IC mixers.